System for calibration of a compressor unit in a heating, ventilation, and air conditioning system

ABSTRACT

The present invention provides for a system for calibrating operation of a compressor unit in a heating, ventilation, and air conditioning (HVAC) system. A measuring device measures an operating parameter of the HVAC system at a position where the measuring device is mounted on a refrigerant line of the HVAC system. The measuring device switches states when the value of the measured operating parameter reaches a switching value. A controller estimates a value of the first operating parameter at the position where the first measuring device is mounted on the refrigerant line, and the controller determines whether the estimated first operating parameter is within a threshold percentage of the switching value.

CROSS-REFERENCED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/185,467, filed on Jun. 17, 2016. U.S. patent application Ser. No.15/185,467 is a continuation of U.S. patent application Ser. No.14,064,865, filed on Oct. 28, 2013. This application relates toco-pending U.S. patent application Ser. No. 14/173,686, entitled SYSTEMFOR CONTROLLING OPERATION OF AN HVAC SYSTEM, filed Feb. 5, 2014. U.S.patent application Ser. No. 15/185,467, U.S. patent application Ser. No.14,064,865 and U.S. patent application Ser. No. 14/173,686 areincorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to calibration systems used in heating,ventilation, and air conditioning (HVAC) systems and, more particularly,to a system for calibrating operation of a compressor unit in an HVACsystem.

The discharge pressure and suction pressure of a compressor in aheating, ventilation, and air conditioning (HVAC) system can be used asa diagnostic tool to troubleshoot problems with the system or to confirmthat the system is operating normally. A model of the discharge pressureand suction pressure may be created from test data in a laboratory ormanufacturing facility.

Once the HVAC system is installed, however, use of discharge pressureand suction pressure as a diagnostic tool is time consuming andexpensive. Trained technicians may manually determine and utilizedischarge and suction pressure in diagnostics. A pressure transducer mayalso be utilized as a tool for determining these pressures. Because oftime and costs involved, suction and discharge pressure cannot often beused in the diagnostic process. What is needed are systems and methodsfor utilizing suction and discharge pressure as diagnostic tools in thecalibration of HVAC systems.

SUMMARY

The present invention provides for a system for calibrating operation ofa compressor unit in a heating, ventilation, and air conditioning (HVAC)system. A controller estimates the value of an operating parameter ofthe HVAC system at a position on a refrigerant line of the HVAC systemwhere a measuring device is mounted to measure the operating parameter.The controller determines whether the estimated operating parameter iswithin a threshold percentage of the value of the operating parameter atwhich the measuring device switches states.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following DetailedDescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates an HVAC system;

FIG. 2 illustrates a compressor assembly and a control assembly;

FIG. 3 shows a flow chart of steps in a method for calibrating operationof a compressor unit in an HVAC system; and

FIG. 4 shows a graph of discharge pressure of a compressor unit versusoutside temperature.

DETAILED DESCRIPTION

In the following discussion, numerous specific details are set forth toprovide a thorough understanding of the present invention. However,those skilled in the art will appreciate that the present invention maybe practiced without such specific details. In other instances,well-known elements have been illustrated in schematic or block diagramform in order not to obscure the present invention in unnecessarydetail. Additionally, for the most part, details concerning well-knownfeatures and elements have been omitted inasmuch as such details are notconsidered necessary to obtain a complete understanding of the presentinvention, and are considered to be within the understanding of personsof ordinary skill in the relevant art.

Referring to FIG. 1, a first compressor unit 102 may be configured tooperate in a heat pump, such as a heat pump system 100. The firstcompressor unit 102 may be configured to compress low pressurerefrigerant in vapor form to a higher pressure vapor. It will beunderstood by persons of ordinary skill that the first compressor unit102 may operate within the heat pump system 100 in conjunction withother known components.

The heat pump system 100 may comprise an outdoor unit 103 operativelyconnected to an indoor unit 105. The outdoor unit 103 may comprise thefirst compressor unit 102 having a suction line 142 and a discharge line140. The suction line 142 and the discharge line 140 may operativelyconnect the first compressor unit 102 with a reversing valve 144 at anoutput port 143 and an input port 141, respectively. The reversing valve144 may be configured to change the direction of flow of refrigerantwithin the heat pump system 100.

A first transfer line 146 may operatively connect a first reversing port147 with an outside heat exchanger unit 148 configured to condense highpressure vapor refrigerant to a liquid. An outdoor fan 166 may beconfigured to blow outside air over the heat exchange section of theoutside heat exchanger unit 148.

A distributor 158 may be operatively connected to the outlet of theoutside heat exchanger unit 148 at a first end 160 and operativelyconnected to the inlet of an outside heater exchanger unit 148 at asecond end 162. Liquid tubing 164 may span the first end 160 and thesecond end 162 for transporting substantially liquid refrigerant fromthe outside heat exchanger unit 148 to an inside heat exchanger unit154. The distributor 158 may function as a metering device to regulatethe amount of liquid refrigerant flowing into the inside heaterexchanger unit 154.

The inside heat exchanger unit 154 may be configured to evaporate liquidrefrigerant to a vapor. An indoor blower 156 may be configured to pullair over coils of the inside heat exchanger unit 154 and to circulateair into the enclosed space. A second transfer line 150 may operativelyconnect a second reversing port 152 with the inside heat exchanger unit154 to transfer refrigerant in low pressure vapor form back into thecompressor unit 102 through the suction line 142.

It will be understood by persons of ordinary skill that operation of theheat pump system 100 may be changed from heating to cooling by reversingflow within the system so that the inside heat exchanger unit 154operates as a condenser and the outside heat exchanger unit operates asan evaporator.

Referring to FIG. 2, a control assembly 110 may be operationally coupledto the first compressor unit 102. The control assembly 110 may comprisean electrical power converter, such as a first inverter 104 and anelectronic first controller 106. The first inverter 104 may beoperationally connected to the first compressor unit 102 and configuredto adjust the input voltage delivered to the first compressor unit 102.

The first inverter 104 may be operationally connected to a firstcontroller 106 configured to receive and send operation signals foroperation of the HVAC system 100. The first controller 106 may be anoutside unit controller.

The first inverter 104 may be operationally coupled to the firstcompressor unit 102 and configured to modify the input voltage deliveredto the first compressor unit 102. The first inverter 104 may beoperationally coupled to a first controller 106 configured to receiveand send control signals for operation of the HVAC system 100.

A compressor speed of the first compressor unit 102 may be controlled bythe first inverter 104 receiving control signals from the firstcontroller 106. It will be understood that the compressor speed may becontrolled without the use of an inverter as part of the controlassembly 110. In those embodiments, the first controller 106 may beconfigured to utilize other known variable-speed solutions, includingbut not limited to pulse width modulation of the compression process, ormodulating the capacity by bypassing some of the refrigerant around thecompression process (referred to as “unloading”).

The control assembly 110 may further comprise other control devices,such as an inside control unit 170 and a thermostat 172. The insidecontrol unit 170 may operate in conjunction with the first controller106 to control operation of the indoor blower 156 and compressor unit102. The thermostat 172 may adjust the target temperature and have othercommonly-used functions to control the environmental conditions of theenclosed space.

Referring to FIG. 1, the HVAC system 100 may further comprise ameasuring device configured to measure an operating parameter of theHVAC system 100. In some embodiments, the measuring device comprises apressure switch 121 mounted on the discharge line 140 configured tomonitor the discharge pressure of the first compressor unit 102. Thefirst controller 106 may be operationally connected to the pressureswitch 121 to control the monitoring process and store data.

The pressure switch 121 may comprise an actuation pressure and a resetpressure. The actuation pressure is the discharge pressure at which theswitch opens or closes from a normal position, and the reset pressure isthe discharge pressure at which the switch returns to a normal position.It will be understood by persons of ordinary skill in the art that thepressure switch 121 may be configured to monitor other pressure valuesor operating parameters in the HVAC system that may be useful in thesystems and methods disclosed in this description, including but notlimited to the suction pressure.

Referring to FIGS. 3 and 4, the first controller 106 may be configuredto perform one or more methods for calibrating operation of the HVACsystem 100. The HVAC system 100 may be configured to operate in acalibration mode. Calibration of the HVAC system 100 may comprise acomparison between a normal operation model 130 of the HVAC system 100and a measured operating parameter of the HVAC system 100. The model 130may characterize normal operation as a function of one or more operatingconditions. The model 130 shown in FIG. 4 was prepared in laboratorytests using an HVAC system having a variable capacity compressor unit of5 tons. It will be understood by persons of ordinary skill in the artthat a model of normal operation may be prepared for different types ofHVAC systems having one or more compressor units of differentcapacities.

In some embodiments, as shown in FIG. 4, the model 130 may comprise acharacterization of the discharge pressure of the HVAC system 100 as afunction of the outside ambient temperature in which the compressor unit102 operates. The model 130 may be compared to a measured value ofdischarge pressure. The comparison may be used for diagnostic purposesor to determine or infer other useful information about the operation ofthe HVAC system 100.

Referring to FIG. 4, a normal operation model 130 of discharge pressureas a function of the outside ambient pressure may comprise a data set132. The data set 132 may comprise one or more pressure curves 134 a -dwhich represent the discharge pressures of the HVAC system at a set ofoutside ambient temperatures expected under normal operating conditionsfor a specific compressor speed where Speed 4 is the maximum speed ofthe compressor, Speed 1 is the minimum Speed of the compressor andSpeeds 2 and 3 are between Speeds 1 and 4. For example, in someembodiments, Speed 1 corresponding to curve 134 d may equal about 22Hertz (Hz); Speed 2 corresponding to curve 134 c may equal about 34 Hz;Speed 3 corresponding to curve 134 b may equal about 46 Hz; and Speed 4corresponding to curve 134 a may equal about 58 Hz. It will beunderstood that range of speed used to characterize the normal operationmodel 130 may vary according to the configuration and capacity of thecompressor used . . . The data set 132 may be stored in a memory of thefirst controller 106.

It will be further understood that other measuring devices may be usedin place of the pressure switch 121 to obtain measured operatingparameters of the HVAC system 100 that would be useful in thecalibration processes disclosed in this description. For example, abimetal temperature switch may be operationally coupled to the HVACsystem and configured to measure a condensing temperature of the outdoorcoil. A data set for normal operation of the HVAC system 100 may bedeveloped as function of at least the condensing temperature in order toallow for a comparison to be made between normal expected operation andthe measured operating parameter.

Referring to FIG. 3, a method for controlling operation of an HVACsystem may comprise a first step 202 of verifying normal operation ofthe system 100. This operation may include verifying that the compressorunit 102 is currently on. In other embodiments, the HVAC system may bein setback or away mode, when demand on the compressor unit 102 is low.

In a second step 204, the controller assembly may verify that theoutdoor temperature is in a calibration range. A calibration range maycomprise a range of temperatures for a given range of operating speedsof the compressor unit 102 at which the pressure switch 121 changesstates. For example, as shown in FIG. 4, the pressure switch 121 may beconfigured to reset at a discharge pressure of about 280 pounds persquare inch gauge (psig) in a first temperature range T1 for a firstspeed range S1 of the compressor unit 102. The pressure switch 121 maybe configured to open at a discharge pressure of about 340 psig in asecond temperature range T2 for the speed range S1 of the compressorunit 102.

In a third step 206, the first controller 106 may initiate a calibrationmode, based on the verification that the outdoor temperature is in thecalibration range. If the temperature is not in the calibration range,then the HVAC system 100 may continue in normal operation (step 202).

In a fourth step 208, the first controller 106 may set the compressorunit 102 to operate at a first operating speed. For example, thecompressor unit 102 may be operated at the Speed 4, which may correlateto a maximum demand on the compressor unit 102. It will be understood bypersons of ordinary skill in the art that the maximum demand will becompressor-specific and will vary based on the configuration and size ofthe compressor.

In a fifth step 210, the compressor unit 102 may be operated for a firsttime period t₁. The time period t₁ may comprise a pre-determined amountof time configured to increase the discharge pressure of the compressorunit 102 by a pre-selected amount. For example, the time period t₁ maycomprise about 5 minutes, which may elevate the discharge pressure byabout 127%, when the compressor unit 102 is operating at the Speed 2 andat an outside temperature of about 90° F.

The time period t₁ may be configured to change the discharge pressure sothat the discharge pressure crosses the threshold at which pressureswitch 121 changes state. For example, operating the compressor unit 102at the Speed 2 for 5 minutes may result in the pressure switch 121actuating.

In step 212, the actuate event of the pressure switch 121 may berecorded in a memory of the first controller 106. If the pressure switch121 does not change states, the first controller 106 may generate asignal (step 214) to the compressor unit 102 to change demand to operatethe compressor unit at a second operating speed. The change in demandmay comprise a pre-selected percentage of change from the initial demandload, where the pre-selected percentage is configured to change thedischarge pressure of the compressor unit 102. In some embodiments, thedischarge pressure is elevated to change the state of the pressureswitch 121.

In step 210, the compressor unit 102 may be operated for a second timeperiod t₂. The time period t₂ may comprise a pre-determined amount oftime configured to change the discharge pressure of the compressor unit102 by a pre-selected amount. It will be understood that the timeperiods t₁ and t₂ may be based on the expected operationalcharacteristics of the HVAC system 100, including but not limited to thecompressor unit capacity.

In step 216, the current operating state of the HVAC system at theactuate event (recorded in step 212) may be recorded in a memory of thefirst controller 106. The operating state may comprise known values ofthe HVAC system 100 and other data readily accessible throughmeasurement by sensors or calculable based on known or measured datawithin the control assembly 110, including data regarding operation ofthe compressor unit 102 taken from the inverter 104.

In step 218, the discharge pressure of the compressor unit 102 may bedetermined based on the operating state. For example, the dischargepressure may be calculated according to the systems and methodsdescribed in U.S. application Ser. No. 14/173,686 entitled “SYSTEM FORCONTROLLING OPERATION OF AN HVAC SYSTEM”, which is here incorporated byreference. In other embodiments, a data set containing acharacterization of discharge pressure, for example in a table format,may be stored in memory and the predicted discharge pressure may bedetermined by correlating one or more parameters of the operating stateof the compressor unit 102 with the stored estimated value of thepredicted discharge pressure. Alternatively, the estimated dischargepressure may be received by the first controller 106 from a separatedevice, including but not limited to a pressure transducer operationallyconnected to the HVAC system.

In step 220, the first controller 106 may compare the calculateddischarge pressure of step 218 to the value of the pressure at which thepressure switch 121 is configured to change states (referred to as the“switch setting”). The first controller 106 may determine whether thecalculated discharge pressure is within a threshold percentage of theswitch setting. In some embodiments, the threshold percentage may be ina range of −10% to +10% of the switch setting. The threshold percentagemay be pre-selected and programmed into the controller 106 based on theacceptable operational tolerances of the HVAC system 100.

In step 222, the first controller 106 may be configured to generate andsend a communication based on whether the calculated discharge pressureis within the pre-selected percentage of the switch setting. Forexample, if the calculated discharge pressure is outside the thresholdpercentage of the switch setting, the first controller 106 may send acommunication indicating that the HVAC system 100 is not operatingwithin acceptable parameters.

The communication may comprise a textual or visual summary of dataregarding operation of the HVAC system 100, including a characterizationof discharge pressure of the compressor unit 102, such as a chart,graph, or table. The communication may be sent to a display, stored inmemory, or communicated directly to a third party. Referring to FIG. 2,the communication may be stored in a memory log 112 operationallyconnected to the first controller 106. The predicted pressure may besent to a display 114. For example, a diagnostician may be connected toa port operationally connected to the controller 106 and may request areading of the predicted discharge pressure, or may access the memorylog 112 that contains a history of the predicted pressure for a giventime period. In other embodiments, the communication generated by thefirst controller 106 in step 222 may be sent via a wireless device, forexample as an email or text message.

In other embodiments, the measuring device, such as the pressure switch121, may be positioned at other positions within the HVAC system 100 forcalibrating the pressure at that position, including but not limited topositioning a pressure switch 120 positioned on the suction line 142 formeasuring suction pressure, as shown in FIG. 1.

Having thus described the present invention by reference to certain ofits preferred embodiments, it is noted that the embodiments disclosedare illustrative rather than limiting in nature and that a wide range ofvariations, modifications, changes, and substitutions are contemplatedin the foregoing disclosure and, in some instances, some features of thepresent invention may be employed without a corresponding use of theother features. Many such variations and modifications may be considereddesirable by those skilled in the art based upon a review of theforegoing description of preferred embodiments. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the scope of the invention.

What is claimed:
 1. A system for calibrating operation of a compressor in a heating, ventilation, and air conditioning (HVAC) unit, the system comprising: a compressor unit; a pressure switch positioned on a discharge line of the compressor unit and configured to measure refrigerant pressure in the discharge line and switch operation of the HVAC unit from a first operating state to a second operating state when a value of the measured refrigerant pressure reaches a first switching value; and a controller configured to estimate a first estimated value of the refrigerant pressure and determine whether the first estimated value is within a first threshold percentage of the first switching value.
 2. The system of claim 1 further comprising: an indoor unit; an outdoor unit operatively connected to the indoor unit; and wherein the outdoor unit comprises the compressor unit, the compressor unit comprising a suction line and the discharge line.
 3. The system of claim 1, wherein the compressor unit operates at an outside ambient temperature.
 4. The system of claim 1, wherein the discharge line comprises a channel for refrigerant flow.
 5. The system of claim 1, wherein the controller is configured to generate a first communication based on a determination of whether the first estimated value is within the first threshold percentage of the first switching value.
 6. The system of claim 5, wherein the controller is configured to send the first communication using a wireless connection with an external device.
 7. The system of claim 5, wherein the controller is configured to determine whether the pressure switch has switched states from the first operating state to the second operating state.
 8. The system of claim 7, wherein: the controller is configured to change demand on the compressor unit from a first load to a second load if the pressure switch has not switched states from the first operating state to the second operating state; and wherein changing the demand comprises changing a speed of the compressor unit.
 9. The system of claim 8, wherein: the controller is configured to initiate a first mode of operation for calibrating operation of the compressor unit, wherein the initiation of the first mode of operation is based on outside ambient temperature; and the controller is configured to operate the compressor unit under the second load for a first time period to change the measured refrigerant pressure of the HVAC system to cause the pressure switch to switch states.
 10. A system for calibrating operation of a compressor in a heating, ventilation, and air conditioning (HVAC) unit, the system comprising: a compressor unit; a temperature switch positioned on a discharge line of the compressor unit and configured to measure refrigerant temperature in the discharge line and switch operation of the HVAC unit from a first operating state to a second operating state when a value of the measured refrigerant temperature reaches a first switching value; and a controller configured to estimate a first estimated value of the refrigerant pressure and determine whether the first estimated value is within a first threshold percentage of the first switching value.
 11. The system of claim 10 further comprising: an indoor unit; an outdoor unit operatively connected to the indoor unit; and wherein the outdoor unit comprises the compressor unit, the compressor unit comprising a suction line and the discharge line.
 12. The system of claim 10, wherein the temperature switch is configured to measure refrigerant temperature at a position where the temperature switch is positioned on the discharge line.
 13. The system of claim 10, wherein the controller is configured to generate a first communication based on a determination of whether the first estimated value is within the first threshold percentage of the first switching value.
 14. The system of claim 13, wherein the controller is configured to determine whether the temperature switch has switched states from the first operating state to the second operating state.
 15. The system of claim 13, wherein: the controller is configured to change demand on the compressor unit from a first load to a second load if the temperature switch has not switched states from the first operating state to the second operating state; and wherein changing the demand comprises changing a speed of the compressor unit.
 16. A method for calibrating operation of a compressor unit in a heating, ventilation, and air conditioning (HVAC) system, the method comprising: mounting a measuring device on a discharge line of the compressor unit, wherein the measuring device is configured to measure at least a first operating parameter of the HVAC system and switch states from a first state to a second state when a value of the measured first operating parameter reaches a first switching value; determining whether the measuring device has switched states from the first state to the second state; and responsive to a determination that the measuring device has not switched states from the first state to the second state, changing demand on the compressor unit from a first load to a second load.
 17. The method of claim 16, wherein changing the demand comprises changing a speed of the compressor unit.
 18. The method of claim 16 further comprising: switching from the first state to the second state when a value of the measured first operating parameter reaches the first switching value; estimating a first estimated value of the first operating parameter; determining whether the first estimated value is within a first threshold percentage of the first switching value; and responsive to a determination that the first estimated value is within the first threshold percentage of the first switching value, generating a first communication; and sending the first communication to an external device using a wireless connection.
 19. The method of claim 16, wherein: the measuring device comprises a pressure switch, and the first operating parameter comprises a pressure of a refrigerant in the discharge line at a position where the measuring device is mounted; and the pressure switch is configured to measure the pressure of the refrigerant at the position where the pressure switch is mounted on the discharge line.
 20. The method of claim 16, wherein: the measuring device comprises a temperature switch, and the first operating parameter comprises a temperature of a refrigerant in the discharge line at a position where the measuring device is mounted; and the temperature switch is configured to measure the temperature of the refrigerant at the position where the temperature switch is mounted on the discharge line. 